Without immediate action, catastrophic and irreversible climate change is surely on its way. That is why December's summit in Copenhagen is so important

Professor Kevin Anderson

The importance of the international climate summit to be held in Copenhagen later this year cannot be over- emphasised; 2009 is literally a make-or-break year in terms of climate-change negotiations. After almost two decades of increasingly heated debate on how to tackle climate change, and notwithstanding the current recession, emissions of global greenhouse gases – from energy use, agriculture, deforestation and industrial processes – are rising at a faster rate now than they have done throughout our history. As we enter the second decade of this new millennium, the international community is faced with a very clear and stark choice: to cut emissions urgently and radically, or to lock the next and future generations into "dangerous climate change".

For far too long now, scientists, politicians, the media and the public, while broadly accepting the science and implications of climate change, have stubbornly refused to acknowledge the scale of rising emissions. So while the rhetoric of low-carbon action has been notched up year after year, the reality is that collectively we have been on a high-carbon binge. Unfortunately, most of the emissions we have put into the atmosphere over the 17 years since the Earth Summit in Rio and the 12 years since the start of the Kyoto process, will remain there for another century – added to, year on year, by our increasingly carbon-profligate lifestyles.

It is this cumulative nature of emissions, whereby the concentration of greenhouses gases builds up in the atmosphere, combined with our abject failure even to curtail emissions' growth rate, that has brought us to this political tipping point. Either our politicians step up to the plate in Copenhagen and agree to implement an immediate reversal in emissions trends, or we consciously accept a continued and rapid build-up of emissions in the atmosphere with all the implications that entails. We no longer have the luxury of lengthy negotiations such as those associated with the Kyoto Protocol.

As for the scale of reductions necessary, again here we have all been party to downplaying the severity of the issue and are now faced with the consequences of this delusion. In this regard I and my colleagues in the scientific community are particularly responsible. For too long we have, with notable exceptions, been reluctant to spell out clearly the true implications of our analysis, instead couching our conclusions as challenging but politically palatable. However the scientific climate congress held in Copenhagen earlier this year, as a prelude to the political event in December, witnessed a sea-change in attitude among many in the scientific community. The message to policy-makers, businesses and the public is unambiguous. Radical reductions are needed now to give us even a small chance of avoiding the 2°C threshold between "acceptable" and "dangerous" climate change.

Putting this into everyday language, the wealthy, OECD, nations need to reduce their total emissions by at least 40 per cent by 2020, including emissions from aviation and shipping, and without buying emission reductions from poorer nations. Complete decarbonisation of the OECD's energy system needs to be in place by 2030. However these figures may be massaged, such reduction rates are incompatible with the current framing of economic growth. New low-carbon technologies are available, but for them to dominate our energy system will take at least two decades, time we simply don't have, as in the interim our emissions continue to build up in the atmosphere. Only once our energy system is carbon-free and our meat-eating substantially curtailed can we again consider seriously having a growing economy – provided it can be reconciled with the other demands of sustainability.

However, even such draconian reductions by the OECD nations leave only limited opportunities for the poor and less-wealthy nations to continue to increase their emissions. Consequently, while emissions in these nations will rise as their welfare improves, this rise needs to be kept to a minimum through comprehensive low-carbon technologies and policies. Ultimately, all nations across the globe will need to establish carbon-free societies over the coming few decades, completely counter to the rapid emission growth we have experienced since 2000.

While much of this rise has been driven by the newly industrialising nations of China and India, the problem to which they are now contributing is one caused by our emissions and to which we still are a major contributor. According to the Department of Food and Rural Affairs (Defra), absolute UK emissions have risen by 18 per cent since 1990, and show no clear of signs of bucking this trend in the near term. The recent and much-heralded US Waxman-Markey Bill requires no reductions by the US even by 2017, and only four per cent by 2020, half that of Japan's eight per cent target. Russia and New Zealand have no 2020 goals and the EU's target, though ambitious relative to others, is not comprehensive, allows for significant buy-out from poorer nations, and even then falls far short of what would be necessary to meet its own 2°C commitments.

Against this backdrop of a failure by any nation or region to demonstrate meaningful leadership, Copenhagen looks also doomed to failure. But this isn't an option. It has to succeed, driving home at least 40-per-cent cuts by 2020 from the world's wealthy countries and putting the poor and less-wealthy nations on to a low-emission-growth pathway. We have all the necessary policy tools and technologies to rise to this challenge. What we need now is political integrity, scientific candour, a public and business community that acknowledges they are part of both the problem and solution, and a press that resists the temptation for polemic headlines instead of honest reporting.